In the past several decades, there has been an interest in sliding rotary vane gas compressors, the interest in these devices being attributable to several factors, including their basic simplicity, comparatively low manufacturing and installation costs, and relatively high volumetric displacement.
These devices have typically involved a rotor containing a plurality of generally radial slots, which slots are disposed in spaced relation about the periphery of the rotor. Such rotor is mounted on a shaft, and disposed in a housing having either a circular or an elliptically shaped cavity. A slidable vane is disposed in each such slot, with these vanes being caused to move outwardly under the influence of centrifugal force at such time as power is applied to the rotor shaft. The outer tips of these vanes are intended to contact the inner walls of the generally elliptically shaped stator cavity and make sealing contact therewith.
As is obvious, the combination of vanes and sidewall is such that a plurality of chambers are in effect defined in the stator cavity, which chambers are constantly changing their respective configurations during rotor rotation. Thus, by providing an inlet in the stator at a location where a given chamber is enlarging, a charge of gas to be compressed can be taken in. Then, during continued rotation of the rotor, this charge of gas is thereafter compressed as the generally elliptically shaped sidewall causes the respective vanes to move inwardly, to decrease the chamber size. By placing one or more exit ports or discharge ports at the location where each chamber has been caused to become quite small, gas under relatively high pressure can be delivered.
Unfortunately, prior art rotary vane gas compressors suffered from several distinct disadvantages, such as high power penalties, and rapid wear at the tips of the vanes because of high loading, this usually being accompanied by insufficient lubrication.
Although the previous design in accordance with the teaching of U.S. Pat. No. 4,521,167 was highly effective and fully functional, nevertheless, it is a fact that should the bearings be even slightly misplaced or displaced from the true centers of this device, this had the tendency to cause the rotor to be even very slightly cocked and therefore displaced from a true and highly desirable circularly perfect orbit. This non-circular orbit prohibits the side of the rotor from rotating in a perfectly flat plane, which results in an undesirable variable height leakage path between the rotor and the end plate. Typical oil film thicknesses are on the order of 0.0005 inches for applications of this nature. Therefore, clearances of 0.0005 inches or greater can cause excessive internal gas leakage, unless the compressor so to speak is "flooded" with lubricating oil. The expense to hold assemblies to tolerances such as 0.0005 inches is increased, however, when hand fitted procedures are required.
With our original design, any ill-fitting aspects of our device tended to decrease volumetric efficiency, and thereby to invite an undesired radial flow of gas.
Accordingly, I have been motivated to provide a vastly superior rotary vane compressor design and sealing arrangement such that internal leakage as a result of manufacturing discrepancies is greatly decreased without any degradation of the power input.